[A-CG40] 沿岸海洋生態系─１．水循環と陸海相互作用

[ACG40-03] 気仙沼舞根湾における再循環性地下水が植物プランクトン動態に及ぼす影響

*中島 壽視¹、楠 隆大¹、高尾 祥丈¹、杉本 亮¹ (1.福井県立大学)

キーワード：再循環性地下水、植物プランクトン、ラジウム同位体

Riverine inputs are often considered as the main terrestrial source of dissolved inorganic nitrogen (DIN), phosphorus (DIP), and silicon (DSi) in coastal seas. However, the fluxes of nutrients through submarine groundwater discharge (SGD) often exceed riverine inputs in different local and regional scale settings. Although the combined effects of riverine and SGD-derived nutrient inputs are crucial for sustaining marine productivity, a difference of nutrient composition in each source may result in a different response of phytoplankton dynamics in coastal seas. In this study, we evaluated the influence of each nutrient source on phytoplankton dynamics in the head of Kesennuma Bay in June, September and November 2018. Using the short-lived radium and radon isotopes, we quantified the contribution rates of four nutrient sources (river water, fresh SGD, recirculated SGD and offshore waters) on surface waters. Simultaneously, we evaluated productivity, biomass, apparent growth rates and species composition of phytoplankton. In brief results, DIP-enriched recirculated SGD affect significant impacts on phytoplankton dynamics. In the presentation, we will discuss more detailed results.